(1) Several parameters of cerebral function were studied as a function of age in male Fischer-344 rats: (a) Local cerebral glucose utilization (LCGU) measured by the 14C-2-deoxy-D-glucose technique (Sokoloff et al., 1977) increased in all brain regions between 1 and 3 mo; decreased in 11 of 19 regions between 3 and 12 mo; but remained unchanged between 12 and 34 mo. (b) Regional cerebral blood flow (rCBF) measured with 14C-iodoantipyrine (Sakurada et al., 1978; Ohno et al, 1979) increased between 1 and 12 mo in anterior but not posterior brain regions, and tended to decline between 12 and 24 mo. (c) In the retina, there were comparable age-associated decreases in outer nuclear layer thickness, number of photoreceptor nuclei and glucose utilization. These decrements were correlated with decreased LCGU in the superior colliculus between 3 and 12 mo. (2) In adult rats, central muscarinic stimulation with oxotremorine caused regional increases in LCGU. (3) GABAergic agonist drugs produced variable decreases in LCGU, but increases in the red nucleus of the adult rat.